It is a servo, and the seller doesn't really seem interested in answering some questions about it, so I was hoping someone on here could shed some light on it.

First, why are there 2 output shafts? Is it just in case its powering something on both sides? Or is it for an encoder? If its for an encoder, can an brand encoder be used or only Maxon? How will I know which type to use?

Second, it is listed as a "servo", yet is also has a 72 RPM no-load rating. I was under the impression that generally, servos don't work like a regular motor, they only adjust their position based on a pulsed input. So why list how many RPMs it can do? Is it possible that this particular motor works both ways?

Third, on the back of the motor it looks like there are only 2 connections, like a normal non-servo motor would have. So, how do you control the angle? Is this why an encoder is needed?

That is just a Gear DC motor, not a servo. It is called a servo motor due to it having the non-geared motor shaft exiting the case for an encoder whereby a Servo control circuit could control this gear motor's speed, acceleration and position.